JPH07283427A - Thin-film solar cell - Google Patents

Abstract

PURPOSE:To prevent deterioration due to ultraviolet ray by adding ultraviolet ray absorbent which is used when laminating a double-sided moisture-proof film. CONSTITUTION:Deformation polyolefin adhesive is used as the adhesives of adhesive layers 61 and 62, where benzotriazol ultraviolet ray absorbent is blended by 2%. The adhesive is applied to a trifluoric ethylene chloride moisture- proof film whose one surface is subjected to corona treatment to form moisture- proof films. The films are used as moisture-proof films 71 and 72 and are set to both sides of a solar battery cell and are laminated under vacuum heating contact bonding conditions to form the thin-film solar cell. The ultraviolet ray absorbent in the adhesive layer absorbs ultraviolet rays and is converted to thermal energy in a molecule for making harmless light energy and hence preventing deterioration due to ultraviolet rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film solar cell using a flexible insulating substrate.

[0002]

2. Description of the Related Art Solar cells have been attracting attention as clean energy, and their technological progress has been remarkable. In particular, since a photoelectric conversion layer mainly composed of amorphous silicon can be easily formed into a large area and is inexpensive, a thin-film solar cell using it is highly expected. Conventional solar cells use glass substrates, but there is a strong demand for thinner and lighter ones because of their thick, heavy, fragile, and workability improvements due to their application to outdoor roofs. ing. To meet these demands, a flexible type thin film solar cell using a flexible plastic film and a thin film metal film as a substrate is being put into practical use. Such flexible type solar cells are
For long-term use for 5 years, a moisture-proof film is laminated on both front and back sides of the solar cell via adhesive layers to prevent moisture from entering. FIG. 1 shows a cross-sectional structure of such a flexible solar cell, which comprises a flexible plastic film substrate 1 on one surface of which a first electrode layer 2 made of metal, an amorphous semiconductor layer 3 having a pin junction, ITO, etc. The transparent second electrode layer 4 is laminated, and the third electrode layer 5 described in, for example, Japanese Patent Application No. 5-67976 is formed on the other surface side, and the through hole opened in the substrate 1 is formed. Is connected to the first electrode layer 2 or the second electrode layer 4 through. The solar cell having such a structure is sandwiched between a transparent moisture-proof film 71 having a transparent adhesive layer 61 on the second electrode layer and a moisture-proof film 72 having an adhesive layer 62 on the third electrode layer 5. It is worn.

[0003]

By the way, in such a conventional thin film solar cell, deterioration of the adhesive due to ultraviolet rays,
Oxidation by oxygen or activation of heavy metal ions in the adhesive due to the influence of heat and oxygen causes the adhesive to change color,
There is a problem that minute cracks and peeling may occur due to a decrease in adhesive strength. These problems are caused by the moisture-proof films 71, 7
2 was large on the entire surface and the mating surface of the end portions of the laminate, particularly the mating surface of the edge portions, which was a factor of reducing the output of the solar cell. Therefore, such a thin film solar cell is not yet practically sufficient, and further improvement has been desired.

An object of the present invention is to solve the above problems and provide a thin film solar cell having excellent moisture resistance and weather resistance.

[0005]

In order to achieve the above-mentioned object, the present invention is to laminate at least a first electrode layer, a photoelectric conversion semiconductor layer, a transparent second electrode layer on a flexible substrate,
A thin-film solar cell sandwiched by a moisture-proof film with an adhesive layer, in which an ultraviolet absorber, an antioxidant and a metal deactivator are added to the adhesive alone or in combination of two or more thereof. And And it is effective that the additive amount in the adhesive is 0.1 to 5% by weight.

[0006]

The ultraviolet absorber in the adhesive layer according to claim 1 absorbs ultraviolet rays and converts them into thermal energy or the like in the molecule to render light energy harmless and prevent deterioration due to ultraviolet rays. The antioxidant according to claim 2 traps radicals generated in the process of oxidative deterioration, and by itself becoming a stable phenoxy radical, a radical chain inhibitor that functions as an antioxidant, and in the process of oxidative deterioration, There are peroxide decomposing agents that function as antioxidants by ionically decomposing the hydroperoxide that is generated and suppressing radical generation, and there are also peroxide decomposing agents that, when used alone or as a mixture, exert a more antioxidant function. The metal deactivator of the third aspect suppresses activation of heavy metal ions of the adhesive and prevents strength deterioration. Further, in the hydrazine-based metal deactivator, since the hindered phenol structure is formed in the hydrazine compound, the antioxidant function is strengthened and strength deterioration due to the influence of heat or oxygen is prevented.

The above-mentioned additives are expected to be effective when used alone, but a synergistic effect may be expected when two to three kinds of them are mixed. However, if the addition amount is less than 0.5% by weight irrespective of whether it is used alone or as a mixture, the respective functions are not fulfilled, and conversely, if it exceeds 5% by weight, the function as an adhesive is deteriorated or discolored.

[0008]

EXAMPLE The structure of a thin film solar cell according to an example of the present invention is also shown in FIG.
Is the same as. The film-like insulating substrate 1 is required to have heat resistance because the electrode layer and the amorphous semiconductor layer are formed at about 200 ° C. Therefore, as the plastic film having heat resistance, polyimide, polyetherimide, polysulfone, polyether sulfone, polyphenylene sulfide, para-type aramid, polyether ketone, fluorine-based general film, but especially polyimide, para-type aramid , General fluorine-based films are suitable. However, a foil of stainless steel, nickel, copper or the like may be used as the thin film metal film, and a heat resistant insulating film may be applied to the surface. The amorphous semiconductor layer 3 is a thin film mainly composed of amorphous silicon having a nip junction, which is generally formed by a CVD method or the like. Electrode layers 2, 4,
As 5, a metal film, a transparent conductive film, and a metal film are formed by means such as sputtering.

As the moisture-proof film 71 on the light-incident side, a transparent plastic film having a low moisture permeability is used. Fluorine series, polymethylmethacrylate,
Examples thereof include films of polyarylate, polyethylene naphthalate, polysulfone, polyether sulfone, polyvinyl chloride, polycarbonate, polyphenylene sulfide, and the like. Further, the moisture-proof film 72 on the side opposite to the light incident side does not necessarily have to be transparent. For example, in addition to the above film, a metal foil of aluminum or the like is sandwiched with a plastic film. Even if the rate is high, a metal foil sandwiched by a plastic film to block intruding water can be used.

The materials used for the adhesive layers 61 and 62 in which the additives are mixed are polyvinyl alcohol, polyvinyl butyral, polyolefin type ethylene-vinyl acetate copolymer (EVA), vinyl chloride copolymer, propylene copolymer. , Acrylonitrile copolymer and the like. The light incident side adhesive layer 61 is preferably transparent. Example 1: This example is an example of claim 1.

A polyimide film (manufactured by Toray DuPont Co., Ltd., trade name: Kapton) is used as the film substrate 1, the first electrode layer 2 is an Ag film, and the amorphous semiconductor layer 3 is n.
The ip junction film, the ITO film as the second electrode layer 4, and the Ag film as the third electrode layer 5 were formed on the back side of the insulating substrate 1 by a predetermined device to form a solar cell. And the adhesive layer 6
Benzotriazole-based ultraviolet absorber as an adhesive for Nos. 1 and 62 (manufactured by Ciba-Geigy, trade name: TINUVIN32
6) was mixed with 2% by weight of a modified polyolefin adhesive and corona-treated on one side with trifluoroethylene chloride (P
CTFE: manufactured by Daikin Co., Ltd., trade name: Daiflon) A moisture-proof film was coated on a moisture-proof film so as to have a film thickness of 50 μm to prepare a moisture-proof film having an adhesive layer. The moisture-proof film provided with this adhesive layer was set on both sides of the solar cell as moisture-proof films 71 and 72, and laminated at a temperature of 130 ° C. for 15 minutes under vacuum heating and pressure bonding conditions to manufacture a thin-film solar cell. Embodiment 2: This embodiment is also the embodiment of claim 1 and embodiment 1
Example 1 except that the moisture-proof film 72 on the back side of the solar cell was changed to a moisture-proof film of a white Tedlar film (manufactured by DuPont, trade name: Tedlar PVF) in which an aluminum foil was sandwiched with polyvinyl fluoride (PVF). A thin film solar cell was prepared in the same manner as in. Embodiment 3: This embodiment is the embodiment of claim 2 and the embodiment 1
Adhesive layers 61, 62 of the above are mixed with 1.5% by weight of a hindered phenolic antioxidant (Sumitomo Chemical Co., Ltd., trade name: Sumilizer BHT), and one side is corona-treated polyphenylene sulfide. (Toray Industries, Inc., trade name: Torelina) A thin film solar cell was produced in the same manner as in Example 1 except that the above adhesive was applied to the moisture-proof film so that the film thickness became 50 μm. Example 4: This is an example of claim 3 in which the hydrazine-based metal deactivator (trade name: Irganox MD-102 manufactured by Ciba-Geigy) is used as the adhesive for the adhesive layers 61 and 62.
4) Ethylene tetrafluoride-propylene hexafluoride copolymer with one side corona treated with 2% by weight mixed
A thin film solar cell was produced in the same manner as in Example 1 except that the above adhesive was applied to a moisture-proof film (manufactured by DuPont Japan, trade name: Teflon FEP) so that the film thickness was 50 μm. Embodiment 5: This embodiment is the embodiment of claim 4, and embodiment 1
In the adhesive of the adhesive layers 61 and 62 of No. 1, a phenolic antioxidant (trade name: Adecatetab AO manufactured by Asahi Denka Co., Ltd.
-60) A thin film solar cell was produced in the same manner as in Example 1 except that 1% by weight was additionally mixed. Embodiment 6: This embodiment is the embodiment of claim 4, and embodiment 5
In the same manner as in Example 1 except that a hydrazine-based metal deactivator (manufactured by Sumitomo Chemical Co., Ltd., trade name: Stabinol BTZ-M) 0.5% by weight was additionally mixed in the adhesive layers 61 and 62. A thin film solar cell was produced. Comparative Example 1: The adhesives of the adhesive layers 61 and 62 of Example 1 were
A thin-film solar cell was produced in the same manner as in Example 1 except that the modified polyolefin adhesive containing no additive was used.

In each of Examples 1 to 6 and Comparative Example 1 described above, a lead wire is drawn out from the electrode of the solar cell to the outside so that the characteristics can be evaluated. The above-mentioned Examples 1 to 6 and Comparative Example 1 were tested by a weather meter as an accelerated test for outdoor exposure.
000H (outdoor exposure equivalent to about 5 years) As a result, Example 1
In Nos. 6 to 6, no change in appearance was observed, and in Comparative Example 1, the surface was slightly yellowed and slightly darker from the mating surface of the end portions of the laminate toward the central portion. Also,
As a result of measuring the conversion efficiency as the output characteristic of the solar cell, the same values as the initial values were shown in Examples 1 to 6, but Comparative Example 1
It was down 1.2%.

From the above, it can be seen that the thin film solar cells of the examples of the present invention are superior in moisture resistance and weather resistance to the comparative examples in terms of appearance and characteristics. In the above examples, the thin film solar cell in which the third electrode layer is formed on the surface of the substrate is used.However, it is clear that it is effective when applied to the thin film solar cell configured only on one surface of the substrate. is there. The ultraviolet absorber mixed as an additive may be a commonly used ultraviolet absorber, and is not limited to a benzotriazole type, but includes a benzophenone type, an acrylate type, a salicylate type, and the like. This UV absorber is 0.1 to 0.1%
It is mixed in the range of 5% by weight. If it is less than 0.1% by weight, the function as an ultraviolet absorber cannot be fulfilled, and conversely, if it is more than 5% by weight, the function as an adhesive is deteriorated or discolored.

The antioxidant mixed as an additive is not limited to the hindered phenol type and the phenol type, and known materials such as hindered amine type, sulfur type and phosphorus type can be used. This antioxidant is for adhesives
It is mixed in the range of 0.1 to 5% by weight. If it is less than 0.1% by weight, it will not function as an antioxidant, and if it is more than 5% by weight, the function as an adhesive will be reduced or it will be discolored.

The metal deactivator mixed as an additive is not limited to a hydrazine type, but a benzotriazole type or the like can be used. This metal deactivator is also 0.1 to 0.1% for the adhesive.
It is mixed in the range of 5% by weight. If it is less than 0.1% by weight, the function as a metal deactivator cannot be achieved, and conversely, if it exceeds 5% by weight, the function as an adhesive is deteriorated or discolored.

[0016]

According to the present invention, the moisture resistance can be improved by mixing the ultraviolet absorbent, the antioxidant or the metal deactivator alone or in a mixture with the adhesive used for laminating the double-sided moisture-proof film. It was possible to obtain a long-life thin-film solar cell having improved weather resistance as well as good properties.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the structure of a thin film solar cell in which the present invention is implemented.

[Explanation of symbols]

 1 Plastic Film Substrate 2 First Electrode Layer 3 Amorphous Semiconductor Layer 4 Transparent Second Electrode Layer 5 Third Electrode Layer 61 Transparent Adhesive Layer 62 Adhesive Layer 71 Transparent Moisture Proof Film 72 Moisture Proof Film

Claims (5)

[Claims] 1. At least a first electrode layer on a flexible substrate,
A thin film solar cell comprising a photoelectric conversion semiconductor layer and a transparent second electrode layer laminated and bonded by a moisture-proof film via an adhesive layer, wherein an ultraviolet absorber is added to the adhesive. 2. At least a first electrode layer on a flexible substrate,
A thin film solar cell comprising a photoelectric conversion semiconductor layer and a transparent second electrode layer laminated and bonded by a moisture-proof film via an adhesive layer, wherein an antioxidant is added to the adhesive. 3. At least a first electrode layer on a flexible substrate,
A thin-film solar cell comprising a photoelectric conversion semiconductor layer and a transparent second electrode layer laminated and bonded by a moisture-proof film via an adhesive layer, wherein a metal deactivator is added to the adhesive. 4. At least a first electrode layer on a flexible substrate,
A photoelectric conversion semiconductor layer and a transparent second electrode layer are laminated and adhered by a moisture-proof film via an adhesive layer, wherein an ultraviolet absorber, an antioxidant and a metal deactivator are included in the adhesive. A thin-film solar cell, characterized by being mixed and added. 5. The thin film solar cell according to claim 1, wherein the additive amount in the adhesive is 0.1 to 5% by weight.